Frank Lopez had misgivings when he heard the slurred and distracted voice on the phone. "I'm not a homecare assistant," he said, hurriedly, but Eric Douglas reassured him that he only needed someone to help with shopping and general errands, so they arranged to meet for a job interview. When Lopez arrived at Douglas's Manhattan apartment on Tuesday, the street was crawling with paparazzi, and Lopez felt a sudden frisson: maybe Eric's father Kirk Douglas, or brother Michael, or even his sister-in-law Catherine Zeta-Jones was visiting. "I thought this was going to be a beautiful experience," he later told the New York Sun. Instead, his prospective employer had been found dead, curled in on himself in a foetal position on the floor, having suffered what the NYPD said yesterday appeared to be a heart attack. And so Eric Douglas died as he had lived: disappointing people because he was not one of his more famous, more successful family members.

The papers, in the days since, haven't had much good to say about him. They have remembered the time he mocked Michael Douglas's role in Basic Instinct by mooning the audience at a New York club. Or the time he was sued for attacking his limo driver. Or the time he was jailed for letting his dog run amok on an American Airlines flight. Then there are the drug convictions for cocaine, the drink-driving, the rehab, the brattish behaviour, the snide references to his diminutive height, and the ultimate, unforgivable fact: that as far as his public was concerned, he failed.

Eric Anthony Douglas was born on June 21 1958, the youngest son of Kirk Douglas, and the second son from his father's second marriage. By the time he was an adult, his half-brother Michael had already won an Oscar (for One Flew Over the Cuckoo's Nest), and his brother Peter and half-brother Joel were producers. Eric has told interviewers that his LA childhood was very lonely - "You end up one kid, one housekeeper and one dog living next to another kid with one housekeeper and one dog" - and though his life can read like one long series of childish sulks and tantrums, not aided by a 20-year addiction to cocaine and prescription drugs, that wasn't always the case.

It has been much repeated this week that Eric Douglas came to London to study at Rada, where he alienated his fellow students by rejecting the local YMCA (his father's advice) and staying at the Dorchester. In fact, Rada has no record of him as a full-time student (he did only a summer course there). Instead, he studied at Lamda from 1980 to 1981.

One of his teachers was the acclaimed director Helena Kaut-Howson. "I'm so glad you called," she says when I ring to ask if she remembers him. "I saw the news, and I thought, my God! It's so sad. Not only sad that he died, but also the way that they dismiss him as if he was just a non-starter. I've been feeling so guilty, because for so long I've been thinking that I've got to get in touch, and get Eric to do something, to prove that he can do things, and I never did."

She directed him in two plays at Lamda, and "in both he was splendid". The first time, she didn't know who he was. "So in a way it made our relationship completely unaffected by any of that." Like all kids, she says, once people knew who he was, he tended to act up. "I know he was unpopular with the other students because they were prejudiced and he responded in the way that was expected ... [but] when he was working with someone who trusted him and he trusted you, there wasn't any of that expectation."

In one of the plays, she recalls, he played the role of a father, "and I remember him phoning his dad, and talking to him about the part, and his father being so happy about it. Eric was so sweet, and so hopeful." Of his relationship with Eric, Kirk once told the Chicago Tribune: "That relationship gets very difficult because he's too much like me. He's hyperactive. I sometimes say to him, 'Loving and hating you is like loving and hating myself.' " In the same interview, Eric said: "We're both perfectionists, energetic, passionate, intense, we make things happen. It makes us difficult to be around." By 1994, however, his father was maintaining that "Eric has inherited all my worst qualities" (he had just kicked a policeman who happened to be a friend of Kirk's). Eric, on the other hand, was still trying to please: "I would just like my parents to see me happy and healthy and productive - before it's too late." Lately the two had found a kind of bad-joke empathy through the fact that both had acquired a speech impediment - Kirk from a stroke, Eric from an accidental overdose of anxiety pills that put him in an eight-day coma in 1999.

Douglas's career film credits make poignant reading. There are nine, ranging from Yellow Dragon in The Golden Child (1986) to "General's son" in Two-Fisted Tales (1991) to Delta Force 3: The Killing Game (1991). But Kaut-Howson suggests that his interests and gifts lay in a very different direction. "He was interested in Polish theatre, which is a very sophisticated and evolved theatre. He didn't go to see the commercial stuff, he went to see the avant-garde stuff. He had always wanted to do Chekhov, to play Konstantin in The Seagull, who is the unhappy son of a mother who is a big star, and when I was running Theatr Clwyd I thought I should do it with him. But other things always take over, and I feel guilty now."

Acting is a cruel profession, she says, and doubly cruel if you come from a family like Douglas's. "I know other such kids, like Olivier's daughter. It's always a problem, rather than a help. It takes somebody really insensitive, with a thick skin. I know some who can use it as an advantage, but sensitive ones really suffer. He was doomed by the fact that he was expected to develop in a certain way."

In the early 90s Douglas finally gave up acting, and turned to comedy (at his first show he was booed off the stage for being drunk). In 1994 he turned up at the Edinburgh festival, claiming he had been promised a slot at the Gilded Balloon; this wasn't the case. Karen Koren, of the Gilded Balloon, was unforgiving. "The criteria of the late slot are that you have got to be funny," she told the Scotsman at the time. "If you are not, you die. I don't book people because of their family connections; I book people on their merit."

Douglas was becoming increasingly difficult to be around, behaving like a prima donna and shamelessly trading on the family name. In 2001 Zeta-Jones, who had already wanted to ban him from attending her wedding, shouted him down for telling a New York audience that "Michael's Jewish and she's Scottish - together they're the world's cheapest couple." "No," she yelled, "I'm Welsh." One of his more memorable gags seems to be "I came down for breakfast in the morning and found my dad in a toga. I said, 'Jesus!' He said, 'No, Spartacus.' "

By last week, Douglas was in worse shape than he had been for a long time. "His hair was totally white. He looked like he gained 150 pounds. He seemed totally strung out," Baird Jones, an art curator at Webster Hall, told the New York Daily News. "We were supposed to go to a couple of galleries, but we could barely get to one. When the cab got stuck in traffic for 10 seconds, he'd be screaming. He said he wanted to get back into acting and stand-up. But it was hard to see who would give him an audition."

Kaut-Howson's last contact with Douglas was a few years ago, when he was trying to put together a New York production of a play that had done well in London. He got as far as a rehearsed reading, but, like nearly everything else, it fizzled out. He wrote to her about it, and enclosed a poem he had written. She remembers very clearly what it said: "I start the day in a happy mood, feeling positive about life, but I see a hole in front of me. I know I should avoid it, but I know I will fall into it. And I do."